Electrode for electrolytic purposes.



P. FERGHLAND & J. NUSSBAUM.

ELECTRODE FOR ELECTROLYTIC PURPOSES. APPLICATION FILED NOV. 5, 1906.

900,502, Patented 7 Oct. 6, 1908.

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h W i! M E I witnesses fnvenzfiora v UNITED STATES PATENT OFFICE.

PAUL FEROHLAND, OF BERLIN, ANDJOSEPH NUSSBAUM, or GHARLOTTENBURG, GERMANY.

' nmc'rnonn non nmcrnomrrrrc mmrosns.

To all whom it may concern:

Be'it known that we, PAUL Emma,

chemist, a subject of the King of Prussia,

lottenbur Germany, have invented certain new and useful Im .rovements in and Con nected with Electro es for Electrolytic Pur- -oses, of which the following is a specication.

This invention relates to improvements in and connected with electrodes for electrolytic purposes.-

In "electrol' ic processes, when it is not desired to dlssolveor destroy the" positive electrode, platinum or artificial carbon or in some cases leador su erficially peroxidized lead are the materia s generally employed for constitutin the ositlve poles. 0 these materials, platmumisapplicable in only few cases-owing to its exorbitant price, although it has been attempted to reduce the quantity of platinum required as much aspossible by using very fine wires fused into glass tubes and conductin the electric currents to the inner ends of t e platinum wires. But even these platinum-glass electrodes are too costl for most purposes and moreover are exceed ingly brittle and easily damaged. .Furthermore there are but few. processes by which platinum. is not more or less dissolved when .1t' is used: as anode,.there being in some cases a loss of precious .metal and in other cases in addition to that defect the cathodic action, as for instance the deposition of zinc, is interfered with. Carbon electrodes on the v other hand are objectionable from another point of view, in that they are oxidized by anodic oxygen'to carbon dioxid. .In consequence, in electroly-zing aqueous solutions of common salt, the chlorinigas obtained is always deteriorated by a considerable percent age of carbon dioxi'd (from 10 to 12:per cent). .Moreover organic chlorincompounds such as chloroform '01" hexachlorid of ben-j'. zone are formed which appear to the-disap-f ointment of the manufacturer when chlorin as to be condensed or when certain organic chlorin compounds have to be produced.-

But the greatest inconvenience from-[the presence of the carbon dioxid results in the? manufacture of bleaching powderifor which chlorin is mostly used; for, owin to a reat part of the lime being saturated y car omc Specification of Letters Patent.

Application filed November 6; 1906. Serial No. 842,140.

Pat-samba. 6, 190a.

acid instead of chlorin, the resulting bleaching powder is not on] of lower percentage, but also far less rea ily preserved than it would be if pure chlorin had been employed.-

Electrochemists have for long looked out for a material capable of being substituted are immediately made non-conducting'by the .formation of chlorin of lead. Peroxid of lead is attacked neither. by oxygen nor by chlorin electrolytically set free on it, as is well known. But inventors who have intended producing electrodes made of peroxid of lead ave not succeeded in discoverin a suitable form or condition 'of this. materia adapted for the purpose in question. It has been pro osed, for instance, to build up electrodes rom litharge pressed into briquets or tiles and to oxidize thev whole by ,an electric current. Such electrodeswould? be .of an exorbitant weight and of relativel F small conductivity, and it would be ver di ficult (or even impossible) to attach re iable contacts to them.

Now an important object ofthe present invention is to produce electrodes of lead peroxid of good mechanical and conductive qualities and to devise a process or processes for obtaining such electrodes in a convenient and inexpensive way. For this purpose wemake the electrodes of that form of peroxid of lead which is deposited on the ositivc pole in electrolyzing lead salt so utions. ;(()nly simple lead salts such as lead nitrate are adapted for the purpose; complex lead compounds such as sodium plumbate LNa O.PbO, obtained by dissolving lead salts iri caustic soda are objectionable). Solutions of lead nitrate are preferred for this purpose. .Goll'oidal substances, .such as gum. st tic or a decoction of linseed, may be add- ;eil to th.e solution of lead nitrate in order to make the deposit more smooth and glossy.

The conductors upon which the lead peroxid isto be deposited may be lates or wires or tubesor rods of any suitab e material; or

rods or tubes coated with a thin layer of platinum or of peroxid of lead itself, ma be employed. These conductors or non-con uctors upon which the. peroxid of lead is deposited may be removed afterwards or not, according as the especial circumstances may require. But when non-conductors are used as carriers of the electrode material, we prefer to let the carriers remain in the electrode, the strength of the latter being considerably increased by the non-conductor forming a kind of core or skeleton in the electrode.

In order to prevent internal tensions or strains in the deposit, it is necessary to control or. direct the process of deposition in such a manner that the deposit may obtain the same thickness and structure at every point and that no bending or buckling of the core or skeleton may occur during the deposition. Therefore when-sheets such as iron or latinum plates are used as a basis for the deposit, the lead peroxid must be deposited equally on both sides of the sheets. Likewise, when wires, rods or cylinders are to be coated with the deposit, the latter must be kept equable all around the wire or rod or the like. We have found that this end is best attained by revolving the wire, rod or cylinder round its own axis during the whole period of deposition. In carrying out our invention, we fill a cylindrical or other suitable vessel of non-conducting material with a strong solution of nitrate of lead containing say 25 percent. of the said salt. Above said vessel we fix horizontally a disk or wheel revoluble on a vertical shaft in suitable bearin s. Concentric to the said shaft, a carbon P0 or other suitable conductor, or a non-conductor the surface of. which has been made conductive, is secured to the revoluble shaft extending nearly to the bottom of the vessel and connected by means of brushes or other slidin contacts with the positive pole of a suitable source of electricity. At some distance from the carbon rod or other conductor forming the anode of the bath, one or more rods or strong wires of copper or any other suitable conductive substance are immersed in the solution and connected with the negative iple of the electric generator thus forming t e cathode or cathodes of the electrolytic bath. 1 The electric current passing through the bath thus arranged may be reguaccompanyin drawing, in which lated so that the current-density at the anode may be about 6 amperes per square decimeter. A smaller or larger current-density may be .used according as the surface of the anodic core or skeleton, or other circumstances, may re uire.

Owing to the e ectrolytic action of the current, lead peroxid is deposited on the anode and crysta s of metallic lead or lead in a compact state when colloidal substances are used are deposited at the cathode or cathodes of the bath. The metallic lead ma be removed at intervals or continuously rom the cathodes preferablyby means of oscillating scrapers or the like, as is enerally known in electrometallur or in the case of colloidal solutions, the p ates or the like on which the compact metallic lead is deposited may be intermittently removed from the bath. Equivalent quantities of lead and lead erox1d bein thus eliminated from the solution, nitric acid is continuously formed. To neutralize the latter and to replace the elements which are recipitated by the current we may introduce continuously or intermittently oxids of lead, carbonate of lead, white lead or litharge or any other suitable lead compounds into the bath. The above mentioned crystals of metallic lead which are easily oxidized in contact with air ma be used for this purpose. These compoun s of lead may be brought together or mixed with :the solution in any suitable way, but we prefer to hang bags filled with lead oxid into the solution to continuously neutralize the same.

When a suflicient thickness of the deposit of lead peroxid isattained, the current is cut off and the anode is removed from the bath. It may be used as an electrode in electrolytic processes just as it comes from the bath, or the inner core or skeleton may be previously removed, if desired. When, for instance, carbon rods are used as a basis for the deposit, the carbon core may be bored or drilled out, so that the electrode of lead peroxid remains in the form of a tube.

In order that the invention may be more clearly understood reference is made to the Figure 1 s ows a suitable apparatus for carryin our process into practice, Fi 2 shows t e electrode from which the con uctor on which the lead peroxid has been deposited has not yet been removed, Fig. 3 is an electrode ready for use, the original conductor havin been removed.

In Fig. 1 1% is a suitable vessel containing a strong solution B of lead nitrate for ex ample. C is a suitable conductor, consisting of any material not attacked by the elece trolytic action, such as for instance iron, platinum or carbon; but we prefer to use carbon rodssuch as are in common use for electric arc lamps. This conductor C is or earthenware is ing the lead deposited on the cathode are not shown.

In Figs. 2 and 3 K K represents the body of the electrode consisting merely of lead peroxid, the center portions being shown broken away; the conductor C is still in the electrode in Fig. 2 and is shown removed in Fi 3 As already mentioned above, conductors or non-conductors may be used or skeleton for the deposit of lead peroxid. When glass or porcelain or common'china to be used, we prefer to coat the same with a thin layer of peroxid in the following manner. The body to be treated is firstly coated with a thin layer containing lead or lead compounds, as for instance by glazing or enameling the same by means of lead oxid. Glass or earthenware bodies coated with the common potters glazing containing lead may be used, or the bodies may be painted or impregnated with a mixture of lead oxid and a suitable binding medium, agglutinant or paste, or if the bodies are porous pulverized peroxid of lead may be rubbed into their surface. The body thus covered with a layer containing lead is then introduced in an oxidizing solution, such as a solution of sodium hypochlorite, whereby the lead oxid is converted into lead peroxid. The oxidation may be completed by electrolytic action. For instance, we dip a rod or tube of glass into a mixture of lead oxid and diluted. glycerin. After the excess of the mixture has been removed by allowing it to drip olf,'the body is dried and then placed in a solution of sodium hypochlorite or bleaching lye. tinue this operation for too long a time, because in this case the hypochlorite begins to decompose owin to a catalytic action and the deposit scales 0 from the glass body. Half a day will be sufficient for the purpose. The

lass body is now dried and its entire length is then heated by means of a blast-flame, whereby the peroxid of lead is partially decomposed and fused together or incorporated with the glass. The body thus prepared is then again placed in a hypochlorite solution for a longer time, say for one or two days, because no further scaling oif is to be feared. A thin layer of conductive peroxid of lead is thus produced which may be strengthened by using the body as an anode in an electrolytic bath of diluted sulfuric acid or the like, the current being passed into the body as a core It is not advisable to con-.

considerable thickness has tricity with a thin by means of a sheet of lead wound round its upper end. This operation may be continued until the coating is thoroughly oxidized and'eonverted into peroxid of lead. The body thus prepared may be further coated with peroxid of lead in a batlrof nitrate of lead justin the same manner as described above. This being done, the deposit appears intimately united with' the glass and the compound electrode may he suddenly dipped into boiling water or when hot into cold water without bursting or cracking.

Having thus described our invention, what we claim as new and desire to secure by Letters Patent is 1. The herein described process for making electrodes for electrolytic purposes, consisting in dipping suitable conductors into a solution of a lead salt to form the anode and the cathode of an electric current, passing an electric current through the said conductors and the solution, until a deposit of considerable thickness has formed on the anode, and then removing the original conductorforming the anode.

2. The herein described process of making electrodes for electrolytic purposes, consisting in coating a non-conductor of electricity with a'thin layer of peroxid of lead and then depositing peroxid of lead upon said layer by dipping the said non-conductor coated with a conducting layer into a solution of a lead salt to form the anode of an electric current, another suitable conductor forming the cathode of the said current, and then passing an electric current'through the said conducting layer, the solution and the conductor forming the cathode.

3. The herein described process for making electrodes for electrolytic purposes, consisting in dipping suitable conductors into a solution of a lead salt to form the anode and the cathode of an electric current, passing an electric current through the said conductors and the solution, until a deposit of considerable thickness has formed .on the anode, and then separating the said deposit from the said conductor forming the original anode.

4. The herein described process for making electrodes for electrolytic purposes, consisting in dipping suitable conductors into a solution of a lead salt to form the anode and the cathode of an electric current, rotating the said anode and at the same time passing an electric current through the said conductors and the solution, until a deposit of formed on the said anode, and then separating the said deposit from the said conductor forming the original anode.

,5. The herein described process for making electrodes for electrolytic purposes, consisting in coating a non-conductor of eleclayer of peroxid of lead and then depositing peroxid of lead upon set our hands in presence of two subscribing said layer by dipping the said non-conductor witnesses. coated with a conducting layer into a solu- PAUL FERCHLAND. tion of a lead salt tohform thiilanodedof an I JOSEPH N USSBAUM. 5 e ectric current anot er suita e con uctor forming the csithode of the said current, Wltnesses for Paul Ferchland' then rotating the said non-conductor and 'at OLDEMAR the same time passing an electric current HENRY IiIAsPER' through the said conducting layer, the solu- Witnesses for Joseph N ussbaum: 10 tion and the said cathode. VINCENT BURES, 4

g In testimony whereof we have hereunto A. DONATI. 

